/*
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at 
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *  
 */

using System;
using java = biz.ritter.javapi;

namespace org.apache.commons.collections
{

    /**
     * Defines a map that allows bidirectional lookup between key and values.
     * <p>
     * This extended <code>Map</code> represents a mapping where a key may
     * lookup a value and a value may lookup a key with equal ease.
     * This interface extends <code>Map</code> and so may be used anywhere a map
     * is required. The interface provides an inverse map view, enabling
     * full access to both directions of the <code>BidiMap</code>.
     * <p>
     * Implementations should allow a value to be looked up from a key and
     * a key to be looked up from a value with equal performance.
     * <p>
     * This map enforces the restriction that there is a 1:1 relation between
     * keys and values, meaning that multiple keys cannot map to the same value. 
     * This is required so that "inverting" the map results in a map without 
     * duplicate keys. See the {@link #put} method description for more information.
     * 
     * @since Commons Collections 3.0
     * @version $Revision$ $Date$
     *
     * @author Stephen Colebourne
     */
    public interface BidiMap : IterableMap
    {

        /**
         * Obtains a <code>MapIterator</code> over the map.
         * <p>
         * A map iterator is an efficient way of iterating over maps.
         * It does not require that the map is stored using Map Entry objects
         * which can increase performance.
         * <pre>
         * BidiMap map = new DualHashBidiMap();
         * MapIterator it = map.mapIterator();
         * while (it.hasNext()) {
         *   Object key = it.next();
         *   Object value = it.getValue();
         *   it.setValue("newValue");
         * }
         * </pre>
         * 
         * @return a map iterator
         */
        //! we do not need declaration, because is in super type
        //MapIterator mapIterator();

        /**
         * Puts the key-value pair into the map, replacing any previous pair.
         * <p>
         * When adding a key-value pair, the value may already exist in the map
         * against a different key. That mapping is removed, to ensure that the
         * value only occurs once in the inverse map.
         * <pre>
         *  BidiMap map1 = new DualHashBidiMap();
         *  map.put("A","B");  // contains A mapped to B, as per Map
         *  map.put("A","C");  // contains A mapped to C, as per Map
         * 
         *  BidiMap map2 = new DualHashBidiMap();
         *  map.put("A","B");  // contains A mapped to B, as per Map
         *  map.put("C","B");  // contains C mapped to B, key A is removed
         * </pre>
         *
         * @param key  the key to store
         * @param value  the value to store
         * @return the previous value mapped to this key
         * 
         * @throws UnsupportedOperationException if the <code>put</code> method is not supported
         * @throws ClassCastException (optional) if the map limits the type of the 
         *  value and the specified value is inappropriate
         * @throws IllegalArgumentException (optional) if the map limits the values
         *  in some way and the value was invalid
         * @throws NullPointerException (optional) if the map limits the values to
         *  non-null and null was specified
         */
        //! we do not need declaration, because is in super type
        //Object put(Object key, Object value);

        /**
         * Gets the key that is currently mapped to the specified value.
         * <p>
         * If the value is not contained in the map, <code>null</code> is returned.
         * <p>
         * Implementations should seek to make this method perform equally as well
         * as <code>get(Object)</code>.
         *
         * @param value  the value to find the key for
         * @return the mapped key, or <code>null</code> if not found
         * 
         * @throws ClassCastException (optional) if the map limits the type of the 
         *  value and the specified value is inappropriate
         * @throws NullPointerException (optional) if the map limits the values to
         *  non-null and null was specified
         */
        Object getKey(Object value);

        /**
         * Removes the key-value pair that is currently mapped to the specified
         * value (optional operation).
         * <p>
         * If the value is not contained in the map, <code>null</code> is returned.
         * <p>
         * Implementations should seek to make this method perform equally as well
         * as <code>remove(Object)</code>.
         *
         * @param value  the value to find the key-value pair for
         * @return the key that was removed, <code>null</code> if nothing removed
         * 
         * @throws ClassCastException (optional) if the map limits the type of the 
         *  value and the specified value is inappropriate
         * @throws NullPointerException (optional) if the map limits the values to
         *  non-null and null was specified
         * @throws UnsupportedOperationException if this method is not supported
         *  by the implementation
         */
        Object removeValue(Object value);

        /**
         * Gets a view of this map where the keys and values are reversed.
         * <p>
         * Changes to one map will be visible in the other and vice versa.
         * This enables both directions of the map to be accessed as a <code>Map</code>.
         * <p>
         * Implementations should seek to avoid creating a new object every time this
         * method is called. See <code>AbstractMap.values()</code> etc. Calling this
         * method on the inverse map should return the original.
         *
         * @return an inverted bidirectional map
         */
        BidiMap inverseBidiMap();

    }
}